This renewal application has two related objectives. One is the detailed analysis by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) of lymphoid cells for the purpose of detecting polypeptides that are abnormally expressed in acute lymphoblastic leukemia (ALL). The analysis will benefit from the increased resolution of 2-D PAGE we have achieved, the development of computer programs for polypeptide spot matching and from the availability of a lymphoid protein database that we have established and that we propose to expand. The second objective consists of detailed investigations of a selected group of polypeptides of interest. We propose to focus initially on four polypeptides detected in ALL in the initial grant cycle, specifically: LT4 (T cell marker found in abundance in T ALL), L4 (common ALL marker), L3 (a polypeptide that is deficient in ALL subtypes associated with poor prognosis), and p18 (a polypeptide present in relatively high amount in ALL but not in other lymphoid proliferating cells examined). An immobilized pH gradient based approach, developed in this laboratory, will be relied upon to generate preparative amounts of polypeptides for sequencing and for monoclonal antibody production. Antibodies will be utilized to determine the occurrence of the corresponding polypeptides in single cells and for screening of samples using a simple one-dimensional electrophoresis technique. These studies are expected to result in a better understanding of the extent to which the pathogenetic process in leukemia is associated with abnormalities in a major constituent of cells through which function is mediated, namely the proteins.